The present invention relates to a seat belt retractor and, in particular, to a seat belt retractor which automatically locks the retractor spool from rotation in a seat belt withdrawal direction upon withdrawal of a predetermined amount of seat belt webbing from the spool.
Seat belt retractors which automatically lock the retractor spool from rotation in a seat belt withdrawal direction upon withdrawal of a predetermined amount of seat belt webbing from the retractor are known. These retractors are used, for example, to lock (cinch) a child seat firmly in an automotive vehicle. Such retractors are shown in U.S. Pat. No. 4,436,255 and in Higbee U.S. application Ser. No. 589,679, filed Mar. 15, 1984.
In the known retractors, the seat belt webbing is wound about a spool. The spool is supported for rotation, and upon withdrawal of the seat belt webbing, the spool rotates in a belt withdrawal direction. A ratchet is fixed to the spool and rotates with the spool. The spool is locked from rotation in the belt withdrawal direction by a pawl which moves into engagement with the ratchet. The pawl is moved into engagement with the ratchet after a predetermined amount of belt withdrawal. In U.S. Pat. No. 4,436,255 and in the aforementioned Higbee application, the pawl is moved into engagement with the ratchet in response to rotation of a cam. The cam is rotated by a drive mechanism which drives the cam upon rotation of the spool.